QuestionHi -- I have a 1975 CB550 K1 that I bought new. I have the original shop and parts manuals. I have attached a sidecar to the bike and I want to change the sprockets to give me about 20% lower gearing. The front sprocket is a 17-tooth, the rear is 34-tooth. I am thinking of going to a 15 front and a 41 rear, but I can't find anything about maximum torque at specific rpm, and how to get the lower gear ratios I want. If you have any suggestions, I would appreciate them. Also, how do I join the VJMC of North America? Thanks!!
AnswerDavid, A CB550 will go about 110mph with stock gearing. I would try to keep a larger sprocket on the front, 16 perhaps, as putting small sprockets on the front is hard on drive chains.
Check the www.sohc4.us site for specs in SOHC fours, including 500-550s. A quick look showed 30.4ft-lb @ 7,500rpm for torque specifications.
Sprocketspecialists.com can make any sprockets you need. With a high-winding four cylinder bike, the torque values are not really high and occur at fairly high rpms, so gearing down is all you can do.
You may have to relocate the rear chain guard mount if you get a really large sprocket on the rear.
Contact the VJMC at www.vjmc.org and I think they can take PAYPAL now for memberships.
Bill Silver
